Inhibitor



252. COMPOSITIONS latented 'Jan. 7,1930

UNITED STATES PATENT OFFICE HARRY P. CORSON, 01' LAKEWOOD, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE GRASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF DELA- WARE INHIBITOR No Drawing.

The present invention relates to inhibitors, their use for controllin the action of acids 1 on s, II1C to processes 0 c eanmg, p1c ing, scaling or removing oxides and other acid soluble deposits from metallic articles.

I have found that certain alkaloids obtained from cinchona bark display the property of inhibiting the action of acids upon base metals, that is to say, acids containing small amounts of my novel inhibitors will not, or only to a slight degree, dissolve such metals with correspondingly lesser evolution of hydrogen.

Cinchona bark contains a number of alkaloids, of which quinine is the most important. The recovery of this alkaloid consists usually in a process whereby the total alkaloids are first extracted from the bark, quinine sulfate is then crystallized out of the crude mixture, leaving an amorphous residue containing the other products; this is then sometimes worked further to extract other less important alkaloids. The amorphous residue remaining after some or all of the crystallizable alkaloids have been removed is known in the trade as quinoidine. This material has at the present time only very limited application.

I have now found that the addition of small amounts of the crude alkaloid mixture, the various pure alkal did'ffiid'fpai'ti cularly the amorphous residu'eknownas" uinoidinc, to a fdilute m'ineralacid prevents 0hr duces considerably the attack of such acids upon base metals without materially impairing the action of the acid upon the non-metallic scale or deposits. leaving a perfectly clean and unaltered metallic surface. Only very small amounts, say, less than about of 1% of the weight of the dilute acid need to be added to show this efi'ect.

Pickling and cleaning of iron and steel articles, scaling of boiler tubes, freeing pipe lines of rust incrustations, are operations com- Application filed August 9, 1928. Serial )16. 295,632.

article. /The addition of a small amount of c ingbona barhglkaloid to the diluted acids used 111 suc operatlons considerably reduces the disadvantages inherent in the use of ordinary acids.

The action of the inhibitor used can easily be shown by measuring the amount of gas evolved from a test piece immersed in plain acid and acid to which a small amount of the inhibitor has been added.

A piece of black mild sheet steel having a total surface are of 8 sq. in. immersed for 20 hours at 25 C. in 34% sulfuric acid containing 0.5% quinoidine evolved 60 cc. of gas, whereas a similar piece treated under the same conditions with plain 34% sulfuric acid produced over 2000 cc. gas.

This result is confirmed by weighing test pieces before and after treatment. No. 28 gauge sheet steel lost, when immersed for an hour at 150 F. in 6% sulfuric acid containing 0.25% quinoidine, about 0.013 lbs. per sq. ft. surface, whereas the same material lost nearly thrice as much, viz, from 0.032 to 0.038 lbs. in plain 6% sulfuric acid under the same conditions. The conditions in this test duplicate closely actual pickling operations.

The cinchona bark alkaloid inhibitors of the present invention can be used admixed with other inhibitors and similar results obtained. Foalit-producting agentsgcanalsoihe added to tliepickling and cleaning baths without interfering with the action of the inhibitor.

It will be understood that my invention is not limited to the materials and conditions mentioned herein, but that it comprises the application of my novel inhibitors to the various operations carried out under various conditions involving the action of acids upon metal articles where it is desired to free the metal from acid soluble incrustations with least possible attack of the metal itself.

I claim:

monly performed with dilute sulfuric or hy; 1. A cleaning and pickling bath for metals oric such acids, an attack of the metal is unavoide able, and this results in a wasteful loss of While the rust, scale, and comprising a dilute mineral acid containing other incrustations are easily removed by a small amount of cinchona harknalkaloid 2. A cleaning and pickling bath for metals comprising a dilute, mineral acid contain- 59 a i an m a as e l as a weake g of the g a m l am un o g n diigg,

' Examine- 

